Effect of post-weld aging on the mechanical and microstructural properties of friction stir welded aluminum alloy 7075

Abstract

Purpose: of this paper is to investigate the effect of post-weld artificial aging on the friction stir welding of Aluminum Alloy 7075 (AA 7075) for a welding condition of 1600 rpm and 100 mm/min using right and left helical screwed pins for two different shoulder diameters. Design/methodology/approach: The method followed is that first artificial aging has been carried out as 24 hours at 125°C. Afterwards, in order to study the effect of post-weld aging on tool geometry, microstructural examination, hardness measurements and room temperature tensile tests have been carried out. Findings: The results show that left helical screw yields higher mechanical properties and hardness values compared to right helical screw when tested at the same shoulder diameter. It has been observed that post weld aging process compensates the hardness decrease observed in as-welded joints; no significant decrease in hardness is obtained throughout the weld region. Research limitations/implications: For future work it can be suggested to vary the post weld aging condition, such as 12 hours at 125°C. Welding and rotation speeds are other parameters affecting the microstructural and mechanical properties; therefore the effect of varying these parameters should be considered. Practical implications: This study has practical implications and direct applicability. It indicates that helix angle rather than shoulder diameter directly affects the quality of the joint. At certain post weld aging conditions, for obtaining a sound welded joint the right tool selection will be of critical importance. Originality/value: The authors have examined the effect of post weld aging for different helix angles and shoulder diameters. It is believed that examination of the effect of the variation of these parameters on the joint quality provides originality to this study.